1. Field of Invention
The invention is in the field of scaffolding.
2. Description of Related Art
Modular scaffolding is a scaffolding system having horizontal scaffold members and vertical scaffold members designed to be clipped or coupled together at a scaffold joint to create a scaffold structure. Once a scaffold structure is assembled, scaffold planks or boards are placed across horizontal scaffold members to create a scaffold deck or working surface. Scaffold planks are usually designed to couple to horizontal scaffold members—generally, the end of each plank has two hook sections, one at each side of the plank, sized to couple with the horizontal scaffold pipe.
A scaffold joint comprises a connector on the vertical scaffold member that is designed to couple or mate with a connector on a horizontal scaffold member, thereby joining together a horizontal and vertical scaffold member. One type of modular scaffold joint uses an end connector positioned on the end of a horizontal member, where the end connector has lip or hook sections. The lip sections are designed to engage or rest on cups or annuli rings positioned on a vertical scaffold member. One such joint is disclosed in U.S. Pat. No. 4,445,307, which discloses a connector positioned on a horizontal scaffold member, where the connector has two vertically spaced hook sections. These hook sections couple with two vertically spaced upstanding ring members located on the vertical scaffold member. To lock the joint in place, the connector includes a wedge that is driven (generally by a hammer) into position below the upper ring member, thereby wedging the ring against the end connector hood section, latching the horizontal member to the vertical member. As used herein, “latching” refers to the action of engaging a horizontal member to a vertical member, where the action of latching resists dislodgement of the horizontal member from the vertical member from an upwardly directed force.
A second type of latching connector is disclosed in U.S. Pat. Nos. 5,078,532 and 5,028,164, hereby incorporated by reference. These patents also show an end connector positioned on a horizontal scaffold member, where the connector has two vertically spaced hooked sections that couple with two vertically spaced upstanding ring members located on the vertical scaffold member. In this device, the latching of the ring members to the hooked sections is accomplished by a deploying a pivoting member or latch, positioned on the end connector, into position below the top ring member. The latch member has a distal end extending beyond the housing, shaped to allow for placement of the distal end beneath a cup or annular ring positioned on a vertical scaffold member. Hence, when latched, the cup or annular ring is trapped between the hook engagement sections of the connector housing and the distal end of the latch member. The latch pivots on a pivot pin, and can be spring loaded to bias the latch into a locking or actuated position.
The proximal end of the latch extends beyond the housing to create a handle, allowing an operator to grasp the handle to actuate or release the latch member. This action allows for hand actuation of the latch for engagement and disengagement, an improvement over the hammer driven wedge of the 4,445,307 patent. The pivoting latch member allows for ease of assembly of a scaffold structure, and the assembled joint retains a degree of play, as this connector lacks the wedging action of the '307 patented device.
A third type of latching mechanism is disclosed in U.S. application Ser. No. 11/738,273, filed Apr. 20, 2007 (hereby incorporated by reference). This application teaches a horizontal scaffold member having an end connector with two hooks or engagement areas, each designed to couple with a ring or annulus located on a vertical member. The connector includes an upper and a lower latch, each the respective upper and lower coupled ring or cup members. The two latches are mechanically coupled allowing for single action operation to engage or disengage both latches simultaneously.
On each of these modular systems, the horizontal and vertical scaffold members are constructed of hollow steel pipe, preferably galvanized pipe. A commonly used pipe is 1¾ inch diameter steel pipe, having ⅛ inch wall thickness. The end connector is fixed to the end of the horizontal pipe scaffold member, usually by welding the connector to the outside of the pipe. Hence, the end of the horizontal scaffold member, at the connector joint, is thicker than the horizontal pipe member (by at least ¼ inch, if ⅛ inch steel is used to construct the connector) due to the presence of the end connector. This increase in thickness is problematic when attaching a scaffold deck.
Scaffold planks or boards are coupled across horizontal members to create a decking or working surface. Scaffold planks used in a modular system are generally a steel plate having two downward directed side channels that provide rigidity to the plank. See FIGS. 8A and 8B. Each end of the plank has a cutout or hook section 500 on each side channel, designed to engage a horizontal scaffold pipe member (e.g. a semicircular cutout to engage a round pipe member). For ease of manufacturing and assembly of a scaffold plank, the plank end side channel cutouts are usually separate metal pieces that are later welded or otherwise joined to the plank's side channels.
The existing scaffold end connector comprises a housing, where the latching, latch pivot pins, springs and spring pivot pins, etc. are generally maintained in the interior of the housing. The housing is manufactured from plate steel using a die to cut and shape the connector form, and several connectors will be cut at the same by the die. See FIG. 6, detailing the shape of the initial die housing layout. Initial action of the die operation cuts the two sides of an end connector housing 600 and 610, which are joined by rear sections 800A and 800B, and also punches holes in the housing sides to accommodate the latch and spring pivot pins. Adjoining end connectors are joined by metal fingers 750 that will be later removed and discarded. After the initial cut, the die operation will also initially shape each end connector into a desired form—the lateral tabs are bent at ninety degrees, the tops sides of the housing 700 will be shaped to resemble a portion of a cylindrical body (for engagement with the exterior of the horizontal pipe member), and the bottom of the two sides are also flared outwardly (to create a larger mouthed hook section for additional surface area support by a cup on a vertical scaffold member). See FIGS. 7A-7C. In the final die operation, the projecting fingers 750 are removed and the two sides of the housing 600, 610 are folded into an opposing relationship (e.g. the two sides are parallel), by folding or bending rear sections 800A and 800B into a “U” configuration (see FIG. 7A). The die operation may take several discrete steps (e.g. punch out general shape, form the cylindrical top ends, and bend the two sides into an opposing relationship).
After the die operation, two formed end connectors are placed in a jig, a horizontal pipe positioned between the two connectors, and a reinforcing brace positioned on each end connector. The assembled horizontal scaffold member is then welded to form a unitary horizontal scaffold member—the bent lateral tabs on each end connector are welded to the opposing housing side (fixedly joining the two sides of the housing together), the horizontal pipe is welded to the cylindrical sections 700 of the connector sides, and the brace is welded to the end connector and the pipe. Given the construction of the joint, welds are required on the front and rear face of the end connector (to join the lateral tabs), and the top and bottom of the pipe (to join the connector to the pipe), as well as two welds required for the brace. The finished welded end connector has an internal space between the two sides of the housing to accommodate placement of the chosen latch device. The springs, pivot pins and latch members are next installed in the end connector interior to create a finished horizontal scaffold member.
The current end connector design is opened on the top of the connector (see FIG. 7A), thereby exposing the pivot pins and latch members to possible damage from debris falling into the open top (such as mortar, screws, etc.) Also, the end connector is formed by bending and stretching portions of the punched connector form—e.g., the two sides of the connector are formed from a single piece of metal and bent into an opposing relationships, while the top of the connector is physically stretched and deformed to form the cylindrical top portions 700. This bending and deformation can cause misalignment of the two opposing sides, creating a twisted end connector with pivot pin holes that do not align properly and with top and bottom hook sections that may be misaligned for proper engagement with the vertical scaffold member. The inventors have found that about 10% of end connectors have twisted sides or other alignment issues that either make the end connector unusable, or requires hand correction, a time consuming operation. A twisted end connector may create safety issues, and such may not be apparent until after the horizontal scaffold member joint is completed and it is discovered that the twisted horizontal scaffold member will not properly engage the cups on vertical scaffold members on one or both ends of the horizontal scaffold member.
Finally, the end connector adjacent to the horizontal pipe 200 is wider than the horizontal pipe (See FIG. 7B). Consequently, scaffold boards cannot be place over the end connector joint, as the hook sections of the scaffold boards 500 are sized for the pipe 200, not the wider joint of top section 700 to pipe 200. Hence, a gap of about three inches is created in the working surface near a vertical scaffold member—that is, the edge of the working surface stops about three inches from a vertical “wall” of a scaffold structure (see FIG. 7B). A new housing is needed that avoids these problems.
Finally, the present hand actuated latching mechanisms, either the single latch or double latch mechanisms, do not provide a secure positive lock. That is, while these latches resist dislodgment by an upward force, a sufficient twisting force may still dislodge a horizontal member from a vertical member. A positive locking latch is also needed.